The present invention relates to a temperature sensor and in particular to a temperature sensor adapted for use in vehicular exhaust systems.
Modern control systems for automotive engines require measurement of the temperature and pressure in the vehicle exhaust system. Accurate measurements of the temperature and pressure of the exhaust system are increasingly important with the desire to improve engine efficiency and reduce exhaust gas emissions and pollutants. As the high temperature environment within an exhaust tailpipe is somewhat hostile, sensors capable of operating in this environment need to be specially adapted.
A typical temperature sensor according to the state of the art comprises a substrate upon which a conducting pattern is provided and a temperature sensitive means is mounted. Typically, the temperature sensitive means is a resistive or piezo resistive device mounted using flip chip technology to thus provide a temperature sensing assembly. The assembly is also usually coated with a suitable conformal coating to enable it to survive the intended environment. Such a device uses various technologies and is thus not necessarily cheap or convenient to manufacture. Furthermore such a device is not symmetrical and can register different temperatures dependant upon the direction of the airflow.
An alternative form of temperature sensor is realised by printing a temperature sensitive means in the form of a resistor onto a ceramic substrate and then covering the resistor by mounting a second ceramic substrate onto the first substrate to cover at least the resistive element. Such an assembly can be cheaper but is still not symmetrical and thus can still register different temperatures dependant upon the direction of the airflow.
It is desirable to provide a temperature sensor that at least partially overcomes or alleviates the above problems.